Mary Benson was born in Pretoria where she received her early education. In 1941 she joined the South African Women’s Army and served in Cairo, Algiers, Italy, Greece and Vienna until 1945.On her return to South Africa, her attitude started shifting from that of traditional prejudice.
In 1951 she worked as secretary to Tshekedi Khama, who was at the time campaigning to have his banishment revoked. In 1952 Benson went on to help establish the Africa Bureau in London and subsequently acted as secretary for the body. In 1957, she was secretary of the fund set up to raise funds for the defence in the Treason Trial.
From this time on, Benson wrote extensively on the leaders and the followers of the liberation struggle in South Africa.
She has published the biographies of Tshekedi Khama and Chief Albert Luthuli. She has also contributed to the publication edited by Marion Friedman, I Will Still be Moved.